Control valve and method for its production

ABSTRACT

The invention relates to a control valve for influencing the action of a pressure medium on a camshaft adjuster of an internal combustion engine. A control valve of said type comprises a valve housing ( 72 ), in which a displaceable control piston ( 71 ) is arranged in a blind bore.  
     According to the invention, the valve housing ( 72 ) is produced with a through bore ( 73 ) instead of a blind bore, into which through bore ( 73 ) a housing insert ( 79 ) is clipped into a groove ( 80 ). The housing insert can serve to support a pressure spring ( 76 ), and can also additionally have recesses, in the region of which the housing insert ( 79 ) serves to form a port, for example to a tank T.

DESCRIPTION

1. Field of the Invention

The invention relates to a control valve for influencing the action of apressure medium on a camshaft adjuster of an internal combustion engine,in particular according to the preamble of claim 1. The inventionadditionally relates to a method for producing a control valve, inparticular according to the preamble of claim 10.

2. Background of the Invention

A control valve for influencing the action of a pressure medium on acamshaft adjuster of an internal combustion engine is known from theapplicant's patent application DE 10 2004 036 096.0, which was notpublished before the priority date of the present application, in whichcontrol valve a control piston is axially displaceable in a blind boreof a valve housing, wherein the action on a spring element is variedwith the displacement of the control piston. The spring element issupported with one foot point on an end side of the control piston andwith the opposite foot point on the base of the blind bore of the valvehousing. The control valve has a pressure medium port, two tank portsand two working ports, which are associated with oppositely-actingworking chambers of a hydraulic camshaft adjuster. In one axial positionof the control piston, in the control valve, a first working port isconnected to a tank port and the second working port is connected to thepressure medium port, so that it is possible to effect an actuatingmovement of the camshaft adjuster during which the working chamber whichis associated with the second working port increases in volume. Inanother axial position of the control piston, the second working port isconnected to a tank port and the first working port is connected to thepressure medium port, so that it is possible to effect an actuatingmovement of the camshaft adjuster during which the working chamber whichis associated with the first working port increases in volume.

OBJECT OF THE INVENTION

The invention is based on the object of simplifying production of thecontrol valve mentioned in the introduction while further ensuring orimproving its functions.

SUMMARY OF THE INVENTION

According to the invention, the object is achieved by means of a controlvalve according to the features of independent patent claim 1. Preferredembodiments of a control valve according to the invention emergecorresponding to the features of dependent patent claims 2 to 9. Afurther solution of the object on which the invention is based isprovided by means of a method according to independent patent claim 10.Embodiments of the method according to the invention emerge fromdependent patent claims 11 to 13.

The invention is based on the realization that the manufacture of thevalve housing with a blind bore for holding the control piston haspotential for optimization. Imprecise manufacture of the position of abase of the blind bore corresponding to the prior art can in somecircumstances influence the function of the control valve, for examplethe foot point of a spring element, an end position of the controlpiston and/or the hydraulic conditions, for which reason the blind boremust be manufactured with a high degree of accuracy. It can additionallybe necessary for the base of the blind bore to have an additionalopening which forms a port, for example a tank port, and for theproduction of which a further bore must be formed in the valve housingin the region of the base of the blind bore. Here, impurities and burrsmust be carefully avoided in the interior of the valve housing which, inan embodiment with a blind bore, is only completely open at one side,since said impurities and burrs can lead, during operation of thecontrol valve, to adverse mechanical effects, increased wear to thepoint of failure of the control valve or of components which arehydraulically connected to the control valve. On the other hand, theproduction of a blind hole requires the use of a special tool, inparticular a reamer, which, for example, makes an additional undercutnecessary in the region of the base of the blind bore. In somecircumstances, this requires an increased installation length of thecontrol valve. In addition, the shape of the end face of the toolpredefines the shape of the base of the blind bore which can beobtained, so that, in some circumstances, integration of furtherfunctions into the base of the blind bore is only possible withdifficulty. For example, the base of the blind bore cannot delimit theactuating movement of the control piston. Such delimitation of theactuating movement of the control piston is, however, of increasedsignificance since, for example, when a predefined end position of thecontrol piston is exceeded, for example as a result of tolerances of thecomponents of the control valve, the hydraulic connection to a port isonly insufficiently opened or closed. Known solutions operate in that anend stop of the control piston is provided by the spring element “beingcompressed fully” for the end stop to be reached, wherein the endposition is however still dependent on tolerances, also in themanufacture of the blind bore.

According to the invention, the previously explained realizations areimplemented in that the spring element is supported not on a base of theblind bore, but rather, by means of the foot point situated at theopposite side from the control piston, on a housing insert. This meansthat both the valve housing and the housing insert can be producedseparately, as a result of which

-   -   further manufacturing possibilities can be utilized,    -   the housing insert can be produced with defined tolerances,    -   the mechanical properties of the housing insert can be        configured in a targeted fashion    -   and there is greater scope for configuring the geometry of the        housing insert than a base of the blind bore.

The embodiment according to the invention having a housing insert makesit possible, for example, for the bore of the valve housing for holdingthe control piston to be formed as a through bore, so that said bore canbe produced more simply and with greater precision, and the formation ofburrs is reliably avoided. The foot point of the spring element is thenexactly predefined by inserting the housing insert into the valvehousing, as a result of which the position of the foot point can bepredefined with high accuracy. On the other hand, for different controlvalves, it is possible in some circumstances for the same valve housingto be used in connection with different housing inserts, differentpositions of the housing insert relative to the valve housing and/ordifferent support locations of the spring element by means of differentgeometries of the housing inserts which are used.

According to a preferred embodiment of the control valve according tothe invention, the housing insert is embodied in a multifunctionalfashion in that, in addition to the support of the foot point for thespring element, said housing insert has recesses through which thepressure medium can pass out of the control valve in order to form aport, in particular a tank port. The production of the recesses in ahousing insert is simplified with respect to such production for thedesign having a blind bore, with additional configuration possibilitiesfor the recesses, for the number of recesses and for their distributionover the housing insert also being provided. By way of example, therecesses can extend inwards from an outer edge of the housing insert, sothat radially outwardly situated webs or spring lips are formed betweenthe recesses, which webs or spring lips can advantageously be used for aconnection between the housing insert and the valve housing, while insome circumstances, a closed central region of the housing insert isprovided in a radially inward region.

There are many possibilities for a connection between the housing insertand the valve housing. For example, the connection can be aform-fitting, force-fitting or cohesive connection. The housing insertcan be pressed or screwed into the valve housing. According to oneparticular proposal for a simple design of the connection of the housinginsert to the valve housing, which connection is also simple to assembleand, if appropriate, to disassemble, the invention proposes that thehousing insert is clipped into the valve housing.

According to a refinement of the invention, in longitudinal section, thehousing insert is approximately in the form of the longitudinal sectionof a hat or of a pot. By elastically deforming the housing insert, the“brim” of the hat or the edge of the pot can be radially compressed andexpanded, so that the edge or brim is clipped into a suitable groove ofan inner lateral surface of the valve housing. Accordingly, formanufacture, only one suitably formed groove, if appropriate with atleast one insertion slope, must be formed in the lateral surface of thevalve housing, while the housing insert can be producedcost-effectively, for example as a sheet metal part or a shaped part.The previously mentioned recesses can be advantageous in promoting theelastic compression and expansion of the edge or of the brim in theradial direction, said recesses forming elastic webs or spring lips asmentioned previously.

According to a further proposal of the invention, the mid-region of thehat is conical, said mid-region adjoining the edge or the brim. Thedesired deformation for clipping the housing insert in can be providedin this case by elastically deforming the conical mid-region and/or bychanging the cone angle of the mid-region. In addition, the conicaldesign of the mid-region offers improved possibilities for mounting thehousing insert into the valve housing, as will be explained in moredetail in the following.

According to a refinement of the invention, in addition to the functionof supporting a foot point of the spring element and the function offorming the recesses for the port, the housing insert fulfills theadditional function of providing a stop for the control piston, in orderto predefine an axial end position of the control piston. This resultsin a defined end position of the control piston, as a result of whichinsufficient desired opening positions to one of the ports are avoided.At the same time, it is possible to avoid the situation where a stop forthe control piston is provided only by the spring element “beingcompressed fully”. The position of the stop can be predefined exactly bymeans of the separately produced housing insert which is inserted intothe valve housing. A spring action and/or damping action for an “impact”of the control piston against the stop can be obtained by suitablyconfiguring the mechanical properties of the housing insert and/or thehydraulic properties in the region of the housing insert.

A particularly compact design is obtained if the control valve issuitable for being integrated into a camshaft. This additionallyresults, in some circumstances, in short hydraulic transmission pathsbetween the control valve and the associated working chambers of thecamshaft adjuster.

To produce a control valve, a bore is initially formed in the valvehousing, said bore being at least of a length which permits it to holdboth a control piston and also a housing insert. In the simplest case,said bore is a through bore with a constant cross section, whereindifferent cross-sectional configurations along the length of the boreare, however, also possible. In a subsequent working operation, a grooveis formed in the bore of the valve housing, into which bore a housinginsert can later be clipped. The housing insert is subsequently radiallycompressed. Said compression preferably takes place in such a way thatthe outer diameter of the housing insert is less than the diameter ofthe bore in that region in which the housing insert is inserted into thevalve housing. In said state, the housing insert is then inserted intothe bore of the valve housing, approximately as far as into the regionof the groove, where the housing insert is then radially expanded, inparticular by means of elastic forces of the housing insert. In the“clipped-in position”, the radially outer edge of the housing insert isultimately received in the groove of the valve housing. The radialcompression and/or the insertion of the housing insert into the groovecan be assisted by means of suitable insertion slopes in the region ofthe valve housing. Alternatively, or in addition, the compression andexpansion can take place using suitable tools.

According to a refinement of the invention, the housing insert has aconical mid-region, wherein the housing insert is radially elasticallyexpanded and compressed by changing the opening angle of the conicalmid-region.

Assembly is particularly simple if the housing insert is held in thecompressed state by means of a tool which “retains” the previouslymentioned reduced opening angle of the cone until the housing insert isarranged in the valve housing at the appropriate position for expansion.

Advantageous refinements of the invention emerge from the dependentpatent claims and from the entire description. Further features can begathered from the drawings—in particular the illustrated geometries andthe relative dimensions of several components with respect to to oneanother and their relative arrangement and operative connection. Thecombination of features of different embodiments of the invention, or offeatures of different patent claims, deviating from the selectedreferences back, is likewise possible and is hereby encouraged. Thisalso relates to features which are illustrated in separate drawingfigures or are mentioned in the description thereof. Said features canalso be combined with features of different patent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In the figures:

FIG. 1 shows a longitudinal section through a device for changing thecontrol times of an internal combustion engine having a pressure mediumcircuit,

FIG. 2 shows a cross section through the device illustrated in FIG. 1,along the line II-II,

FIG. 3 shows a longitudinal section through a control valve,

FIG. 4 shows a longitudinal section through a second embodiment of acontrol valve,

FIG. 5 shows a longitudinal section through a third embodiment of acontrol valve,

FIG. 6 shows a longitudinal section though a fourth embodiment of acontrol valve,

FIG. 7 shows a longitudinal section through a further embodiment of acontrol valve,

FIG. 8 shows the control valve according to FIG. 7 in an end positionpredefined by a housing insert,

FIG. 9 shows a front view of a housing insert,

FIG. 10 shows a longitudinal section of a housing insert and

FIG. 11 shows an assembly step for inserting the housing insert into thevalve housing with a tool for holding the housing insert in a compressedstate.

DETAILED DESCRIPTION OF THE DRAWING

FIGS. 1 and 2 show a device 1 for changing the control times of aninternal combustion engine. The device 1 substantially comprises astator 2 and a rotor 3 which is arranged concentrically with respectthereto. A drive wheel 4 is rotationally fixedly connected to the stator2 and in the illustrated embodiment is embodied as a sprocket.Embodiments of the drive wheel 4 as a belt or as a gearwheel arelikewise conceivable. The stator 2 is rotatably mounted on the rotor 3,wherein in the illustrated embodiment, five recesses 5 which are spacedapart from one another in the circumferential direction are provided onthe inner lateral surface of the stator 2. The recesses 5 are delimitedin the radial direction by the stator 2 and the rotor 3, in thecircumferential direction by two side walls 6 of the stator 2, and inthe axial direction by a first and a second side cover 7, 8. Each of therecesses 5 is closed off in a pressure-tight manner in this way. Thefirst and second side covers 7, 8 are connected to the stator 2 by meansof connecting elements 9, for example screws.

Axially running vane grooves 10 are formed on the outer lateral surfaceof the rotor 3, with one radially extending vane 11 being formed in eachvane groove 10.

One vane 11 extends into each recess 5, with the vanes 11 bearingagainst the stator 2 in the radial direction and against the side covers7, 8 in the axial direction. Each vane 11 divides a recess 5 into twopressure chambers 12, 13 which act counter to one another. In order toensure that the vane 11 bears against the stator 2 in a pressure-tightmanner, leaf spring elements 15 are attached between the groove bases 14of the vane grooves 10 and the vanes 11, said leaf spring elementsexerting a force on the vanes 11 in the radial direction.

The first and second pressure chambers 12, 13 can be connected via acontrol valve 18 to a pressure medium pump 19 or to a tank 20 by meansof first and second pressure medium lines 16, 17. This forms anactuating drive which permits a relative rotation of the stator 2 withrespect to the rotor 3. Here, it is provided either that all the firstpressure chambers 12 are connected to the pressure medium pump 19 andall the second pressure chambers 13 are connected to the tank 20, orthat the connections are in the exact opposite configuration. If thefirst pressure chambers 12 are connected to the pressure medium pump 19and the second pressure chambers 13 are connected to the tank 20, thefirst pressure chambers 12 expand at the expense of the second pressurechambers 13. This results in a displacement of the vanes 11 in thecircumferential direction, in the direction illustrated by the arrow 21.The rotor 3 is rotated relative to the stator 2 as a result of thedisplacement of the vanes 11.

In the illustrated embodiment, the stator 2 is driven by means of acrankshaft chain drive (not illustrated) which engages on the drivewheel 4 of said stator 2. It is likewise conceivable for the stator 2 tobe driven by means of a belt drive or toothed drive. The rotor 3 isconnected to a camshaft (not illustrated) in a force-fitting,form-fitting or cohesive fashion, for example by means of a press fit orby a screw connection by means of a central screw. The relative rotationof the rotor 3 with respect to the stator 2, as a consequence of theinlet or outlet of pressure medium into or out of the pressure chambers12, 13, results in a phase shift between the camshaft and thecrankshaft. Targeted inlet and outlet of pressure medium into thepressure chambers 12, 13 can therefore be used to vary the control timesof the gas exchange valves of the internal combustion engine in atargeted fashion.

In the illustrated embodiment, the pressure medium lines 16, 17 areformed as substantially radially arranged bores which extend from acentral bore 22 of the rotor 3 to the outer lateral surface thereof. Acentral valve (not illustrated) can be arranged within the central bore22, by means of which central valve the pressure chambers 12, 13 can beconnected to the pressure medium pump 19 or the tank 20 in a targetedfashion. A further option is to arrange a pressure medium distributorwithin the central bore 22, which pressure medium distributor connectsthe pressure medium lines 16, 17 via pressure medium ducts and annulargrooves to the ports of an externally attached control valve 18.

The substantially radially running side walls 6 of the recesses 5 areprovided with moldings 23 which extend into the recesses 5 in thecircumferential direction. The moldings 23 serve as stops for the vanes11 and ensure that the pressure chambers 12, 13 can be supplied withpressure medium even when the rotor 3 assumes one of its extremepositions relative to the stator 2, in which position the vanes 11 bearagainst one of the side walls 6.

In the event of insufficient pressure medium supply to the device 1, forexample during the starting phase of the internal combustion engine, therotor 3 is moved relative to the stator 2 in an uncontrolled fashion asa result of alternating and drag torques which the camshaft exerts onsaid rotor 3. In a first phase, the drag torques of the camshaft pushthe rotor relative to the stator in a circumferential direction whichopposes the rotational direction of the stator, until said rotor andstator come into contact at the side walls 6. Subsequently, thealternating torques which the camshaft exerts on the rotor 3 lead toreciprocating oscillation of the rotor 3 and therefore of the vane 11 inthe recesses 5, until at least one of the pressure chambers 12, 13 iscompletely filled with pressure medium. This leads to increased wear andto noise generation in the device 1. In order to avoid this, a lockingelement 24 is provided in the device 1. In addition, a pot-shaped piston26 is arranged in an axial bore 25 of the rotor 3, which pot-shapedpiston 26 is acted on with force in the axial direction by means of aspring 27. The spring 27 is supported at one side in the axial directionon a ventilation element 28 and is arranged with its remote axial endwithin the pot-shaped piston 26. A slotted guide 29 is formed in thefirst side cover 7 such that the rotor 3 can be locked, relative to thestator 2, in a position which corresponds to the position duringstarting of the internal combustion engine. In said position, the piston26 is pushed into the slotted guide 29 by means of the spring 27 whenthere is insufficient pressure medium supply to the device 1. Inaddition, means are provided to push the piston 26 back into the axialbore 25, and therefore to release the locking, when there is sufficientpressure medium supply to the device 1. This is conventionally achievedby means of pressure medium which is conducted via pressure medium lines(not illustrated) into a cut-out 30 which is formed on the cover-sideface end of the piston 26. In order to be able to conduct leakage oilout of the spring space of the axial bore 25, the ventilation element 28is provided with axially running grooves, along which the pressuremedium can be conducted to a bore in the second side cover 8.

FIG. 1 additionally illustrates the pressure medium circuit 31. Apressure medium port P of a control valve 18 is supplied with pressuremedium from a tank 20 by means of a pressure medium pump 19. At the sametime, pressure medium is conducted from the control valve 18 into thetank 20 via a tank port T. The control valve 18 additionally has twoworking ports A, B. The control valve 18 can be placed in 3 positions bymeans of an electromagnetic actuating element 32 which acts counter tothe spring force of a first spring element 33. In a first position ofthe control valve 18, which corresponds to a state of the actuatingelement 32 in which no electrical current is supplied, the working portA is connected to the tank port T and the pressure medium port P isconnected to the working port B and therefore to the second pressurechamber 13. In a middle position, both the working port A and theworking port B are disconnected both from the pressure medium port P andfrom the tank port T. In a third position of the control valve 18, thepressure medium port P is connected to the working port A andconsequently to the first pressure chamber 12, while the second pressurechamber 13 is connected to the tank port T via the working port B.

FIG. 3 illustrates a control valve 18 in longitudinal section. Thesubstantially hollow cylindrical valve housing 34 is provided with aradial pressure medium port P, a radial tank port T₁, two working portsA, B and an axial tank port T₂. The radial ports P, T₁, A, B are formedas first annular grooves 35 which are spaced apart from one anotheraxially and are formed in the outer lateral surface of the valve housing34. The first annular grooves 35 are provided with a plurality of firstopenings 36 which open out into the interior of the valve housing 34.

A control piston 37 which is likewise of substantially hollowcylindrical form is arranged in an axially displaceable fashion withinthe valve housing 34. One axial end of the control piston is delimitedin a pressure-tight fashion by means of a wall section 37 a. The wallsection 37 a can be formed in one piece with the control piston or canbe formed separately from the latter. The control piston 37 can beplaced and held in any desired position within two extreme values,counter to the spring force of the first spring element 33, by means ofan actuating element 32 (not illustrated).

The outer lateral surface of the control piston 37 is provided with asecond, a third and a fourth annular groove 38, 39, 40. The second andthe third annular grooves 38, 39 communicate with the interior of thecontrol piston 37 via second and third openings 41, 42. The secondannular groove 38 is formed in such a way that it communicates with thefirst openings 36 of the first annular groove 35 of the pressure mediumport P in all positions of the control piston 37 relative to the valvehousing 34.

During operation of the internal combustion engine, pressure mediumpasses from the pressure medium port P, via the second annular groove 38and the second openings 41, into the interior of the control piston 37.In the first position of the control piston 37, illustrated in FIG. 3,the pressure medium passes via the third openings 42 and the thirdannular groove 39 to the working port B. As a result of the action ofpressure medium on the second pressure chambers 13 via the working portB, pressure medium is pushed out of the second pressure chambers 12 tothe working port A, and passes to the axially arranged tank port T₂ viathe first openings 36 of said working port A.

If the electromagnetic actuating element 32 is supplied with electricalcurrent, the control piston 37 is displaced counter to the spring forceof the first spring element 33. As a result, the overlap of the firstopenings 36 of the working port B by a first control edge 43 of thethird annular groove 39 increases. The overlap of the first openings 36of the working port A by a second control edge 44 of the control piston37 likewise increases. When the control piston 37 reaches a middleposition (not illustrated), the working port A is no longer connected tothe axial tank port T₂ as a result of complete overlap of the secondcontrol edge 44. In addition, neither the working port A nor the workingport B communicates with the third annular groove 39. Alternatively, thecontrol piston 37 can be designed in such a way that, in the middleposition, both working ports A, B communicate with the third annulargroove 39.

If the control piston 37 is displaced further counter to the springforce of the first spring element 33, a third control edge 45 unblocksthe first openings 36 of the working port A to the third annular groove39. Pressure medium which flows in from the pressure medium port P nowpasses only to the working port A. At the same time, the fourth annulargroove 40 communicates both with the working port B and with the radialtank port T_(l). In this way, pressure medium passes from the pressuremedium pump 19 into the first pressure chambers 12 which leads to arelative rotation of the rotor 3 with respect to the stator 2. Thepressure medium which is pushed out of the second pressure chambers 13passes via the working port B and the fourth annular groove 40 to theradial tank port T₁. The third control edge 45 and the fourth annulargroove 40 can be formed in such a way that, during displacement of thecontrol piston 37, the working port A is initially connected to thepressure medium pump 19 and the working port B is then connected to thetank 20. Alternatively, both connections can be produced at the sametime.

A substantially cylindrical filter 46 is arranged within the controlpiston 37. The filter 46 comprises a frame 47, preferably made fromplastic, and at least one filter section 48. The filter section 48 ispreferably composed of a mesh of plastic or metal, with the frame 47being non-detachably connected to the filter sections 48. At the axialends of the filter 46, the frame 47 has in each case one substantiallycircular segment 49, with the circular segments 49 being connected toone another by means of a plurality of longitudinal struts 50. Thefilter 46 is fixed within the control piston 37 in a force-fittingfashion by means of the circular segments 49. Here, it is advantageousto form an axial stop 51 within the control piston 37, said axial stop51 serving as a travel delimitation when pressing the filter 46 into thecontrol piston 37. Alternatively, the filter 46 can be pressed in in amanner which is controlled in terms of travel.

The filter 46 is arranged in the region of, and completely overlaps, thesecond openings 41. The filter 46 bears, at one of its axial ends,against the axial stop 51. The other axial end rests on a pot-shapedsleeve 52 which is fixed in the interior of the control piston 37 in aforce-fitting manner. This ensures that the filter 46 maintains itsposition during operation of the internal combustion engine.

The sleeve 52 additionally closes off the control piston 37 in the axialdirection and can serve as an engagement point of a plunger rod (notillustrated) of the actuating element 32.

The circular segments 49 of the filter 46 are connected in the radialdirection to an inner lateral surface 53 of the control piston 37 in apressure-tight manner, while a gap 54 is provided between thelongitudinal struts 50 and the inner lateral surface 53.

Pressure medium flowing in from the pressure port P passes via thesecond openings 41 into an annular groove which is formed between thefilter sections 48 and the inner lateral surface 53 and runs around thefilter 46. The pressure medium passes via the filter sections 48 intothe interior of the control piston 37, as a result of which anyimpurities which are present in the pressure medium are effectively keptaway from the control edges 43, 44, 45.

FIG. 4 illustrates a further embodiment of a control valve 18. Thedesign and function of said variant are approximately identical to thefirst embodiment. In contrast to the first embodiment, no axial stop 51is formed in the inner lateral surface 53 of the control piston 37 here.During assembly of the control valve 18, the filter 46 is pressed intothe control piston 37 in a manner which is controlled in terms oftravel. In said embodiment, a non-return valve 55 is arranged betweenthe filter 46 and the working ports A, B. Said non-return valve 55comprises a housing 56 which is arranged within the control piston 37 ina force-fitting manner. A blocking body 57, which is pressed into a seat59 of the non-return valve 55 by means of a second spring element 58, issituated within the housing 56. Instead of the ball non-return valveillustrated here, other embodiments, for example a plate non-returnvalve, can also be used.

Pressure medium flowing into the control valve 18 passes to thenon-return valve 55 after passing through the filter 46. As a result ofthe arrangement of the filter 46 directly downstream of the pressureport P, the control edges 43, 44, 45 and the non-return valve 55 areeffectively protected from damage on account of dirt particles in thepressure medium. Above a certain pressure within the control piston 37,the blocking body 57 is displaced counter to the spring force of thesecond spring element 58, and pressure medium can pass to the workingports A, B via fourth openings 60, which are formed in the housing 56,and the third openings 42.

During operation of the internal combustion engine, pressure pulsationsare generated within the device 1 as a result of alternating torques ofthe camshaft. In the process, pressure peaks occur which are transmittedinto the hydraulic system and can damage other consumers. Thearrangement of a non-return valve 55 between the pressure chambers 12,13 and the pressure medium port P prevents transmission of said pressurepeaks into the hydraulic system. This protects both the pressure mediumpump 19 and further consumers which are connected to said pressuremedium circuit. In said embodiment, the non-return valve 55 isadvantageously arranged within the control piston 37, and thus requiresno additional installation space. A further advantage is that,specifically when using the control valve 18 as a central valve, thepath between the location at which the pressure pulsations are generatedand the non-return valve 55 is a minimum. Pressure fluctuations areintercepted practically at the point of generation.

FIG. 5 illustrates a further embodiment of a control valve 18. Thedesign and function of said control valve 18 are approximately identicalto the variant shown in FIG. 4. In this embodiment, the filter 46 isadvantageously arranged within the housing 56 of the non-return valve55. The housing 56 can be embodied as a cost-effective plastic shapedpart. By integrating the filter 46 into the housing 56 of the non-returnvalve 55, the assembly outlay when assembling the control valve 18 isreduced considerably. Only one component must now be positioned andfastened within the control piston 37.

In this embodiment, that face end of the control piston 37 which facesaway from the tank port T₂ is formed such that it is closed off. Thehousing 56 is H-shaped in longitudinal section, with the filter 46 beingarranged in one chamber of the H and the blocking body 57 with thesecond spring element 58 being arranged in the other chamber. The secondspring element 58 is supported on a closure 61. The radially runningpart of the housing 56 is provided with an opening which is matched tothe blocking body 57 and serves as a seat 59.

FIG. 6 shows a fourth variant of a control valve 18, in which a controlpiston 37 is arranged in an axially displaceable fashion within asubstantially hollow cylindrical valve housing 34. The control piston 37is likewise of substantially hollow cylindrical design, with that endside which faces toward the axially aligned pressure medium port P beingformed such that it is open. The outer lateral surface of the controlpiston 37 is provided with a first annular groove 35 and a group offirst openings 36.

During operation of the internal combustion engine, pressure mediumpasses into the interior of the valve housing 34 via the axially alignedpressure medium port P. Depending on the position of the control piston37 within the valve housing 34, the pressure medium passes either viasecond openings 41 to the working port B or via third openings 42 to theworking port A. At the same time, the respective working port A, B whichis not being acted on by pressure medium is connected via the firstannular groove 35 to the tank port T.

A filter 46 is arranged between the pressure medium port P and theworking ports A, B. The filter 46 is formed in the shape of a pot andcomprises a frame 47 and filter sections 48. At the side which facestoward the pressure port P, the frame 47 is provided with a radiallyextending collar which serves as an axial stop of the filter 46. Inaddition, it is possible to fix the filter 46 to the valve housing 34 ina form-fitting, force-fitting or cohesive manner. As in the embodimentsdescribed previously, a non-return valve 55 can also be arranged betweenthe pressure medium port P and the working ports A, B here.

A control valve 70 according to the invention has a control piston 71which is arranged in a valve housing 72 in an axially displaceablefashion. The control valve 70 and the control piston 71 are, forexample, formed corresponding to one of the exemplary embodimentsillustrated in FIGS. 1 to 6. However, the bore 73 of the valve housing72 is formed according to FIG. 7 as a through bore of constant diameter,with end-side chamfers 74, 75 which widen outwards. A pressure spring76, which substantially corresponds to the spring element 33 in theexemplary embodiments of FIG. 1 to FIG. 6, has a foot point 77, which issupported on an end side of the control piston 71, and a foot point 78,which is supported on a housing insert 79. The housing insert 79 isclipped into a groove 80 of the inner lateral surface 81 of the valvehousing 72. In the region of that end face of the control piston 71which bears against the foot point 77, the control piston 71 radiallysurrounds the pressure spring 76 by means of an annular shoulder 82,resulting, in some circumstances, in the pressure spring 76 beingguided. In addition, a stop 83, here having an annular stop face,projects from the annular shoulder 82 in the direction of the housinginsert 79, said stop 83 coming into contact with the housing insert 79in the end position of the control valve 70 as illustrated in FIG. 8.

FIG. 9 shows a front view of the housing insert 79, while FIG. 10 showsa longitudinal section of the housing insert 79. The housing insert 79is substantially of pot-shaped or hat-shaped form with

-   -   a circular brim 84 having a radially outer edge 85 which is        received in the groove 80,    -   a conical mid-region 86 and    -   an approximately circular central region 87.

As illustrated in FIG. 7, the pressure spring 78 is held in themid-region 86, so that, in some circumstances, the housing insert 79 canradially guide the pressure spring 76. According to FIG. 9, threenotches or recesses 88 extend radially inwards from the edge 85, saidnotches or recesses 88

-   -   being approximately rectangular in the exemplary embodiment        illustrated in FIG. 9,    -   ending approximately in the central region 78 or the edge        thereof and    -   being uniformly distributed about the circumference.

Annular corners 89 or tapers are provided in the transition regionbetween the recesses 88 and the edge 85, said annular corners 89 ortapers, together with the rest of the design of the housing insert 79,being intended to prevent the housing insert 79 becoming jammed in thevalve housing during assembly. The conical mid-region 86 has an openingangle 90. For elastic radial compression of the housing insert 79, theopening angle 90 is reduced and/or the mid-region 86 is elasticallydeformed. During radial expansion for clipping the housing insert 79into the groove 80, the opening angle 90 increases again.

The housing insert 79 is preferably inserted into the valve housing 72using a tool 91 according to FIG. 11. The tool 91 is rotationallysymmetrical about the longitudinal axis 95-95. The tool 91 has a centralblind bore which can be of cylindrical or conical form. In each case,the opening angle of the blind bore 92 is less than the opening angle 90of the housing insert 79 in the expanded state. Consequently, theconical mid-region is radially outwardly pressed against the inner faceof the blind bore and is held therein in a force-fitting manner.Accordingly, the housing insert 79 can be inserted in the radiallycompressed state into the blind bore 92, with the outer diameter of thehousing insert 79 approximately corresponding to the diameter of thebore 73 or being less than said diameter. In said state, the housinginsert 79 can be inserted into the valve housing 72 by means of the tool91, as illustrated in FIG. 11. Here, a shoulder 93 of the tool 91 canpredefine how far the tool 91, with the housing insert 79, can be pushedinto the valve housing 72. When the housing insert 79 is approximatelyin the region of the groove 80, the housing insert 79 can be pushed outof or ejected from the tool 91. Here, an ejecting force can be exertedon the housing insert 79 by means of an auxiliary device which isinserted into a longitudinal bore 94 which opens out into the blind bore92. If the blind bore 92 is conical rather than cylindrical, the radialouter diameter of the housing insert 79 can be increased continuouslywith displacement.

The recesses 88 form a flow cross section to the port, for example inthe direction of the tank. Here, a suitable selection of the ratiobetween the flow cross sections at port B in the control valve 70 andthe recesses 88 is significant. If the outflow cross section, which ispredefined by the recesses 88, is too small relative to the flow crosssections of the other ports involved, an undesired dynamic pressure canbuild up in the valve.

In an assembly process, the housing insert 79 can be suppliedcontinuously, for example by means of an oscillating conveyer. Throughsuitable selection of the geometry of the housing insert, of the sheetmetal thickness, and by specifying the curvatures and the opening angle90 as well as the material and suitable material treatment processes,the force required for deforming the housing insert 79 and the securingeffect which can be obtained by clipping the housing insert 79 into thegroove 80 can be structurally predefined. The mechanical strength of thehousing insert 79 and/or the surface hardness, in particular in thesupport region of the pressure spring 76, is preferably increased bymeans of case-hardening and tempering.

LIST OF REFERENCE SYMBOLS

1 Device

2 Stator

3 Rotor

4 Drive wheel

5 Recesses

6 Side wall

7 First side cover

8 Second side cover

9 Connecting element

10 Vane groove

11 Vane

12 First pressure chamber

13 Second pressure chamber

14 Groove base

15 Leaf spring element

16 First pressure medium line

17 Second pressure medium line

18 Control valve

19 Pressure medium pump

20 Tank

21 Arrow

22 Central bore

23 Moldings

24 Locking element

25 Axial bore

26 Piston

27 Spring

28 Ventilation element

29 Slotted guide

30 Cut-out

31 Pressure medium circuit

32 Actuating element

33 First spring element

34 Valve housing

35 First annular groove

36 First openings

37 Control piston

37 a Wall section

38 Second annular groove

39 Third annular groove

40 Fourth annular groove

41 Second opening

42 Third opening

43 First control edge

44 Second control edge

45 Third control edge

46 Filter

47 Frame

48 Filter section

49 Segment

50 Longitudinal struts

51 Axial stop

52 Sleeve

53 Lateral surface

54 Gap

55 Non-return valve

56 Housing

57 Blocking body

58 Second spring element

59 Seat

60 Fourth opening

61 Closure

70 Control valve

71 Control piston

72 Valve housing

73 Bore

74 Chamfer

75 Chamfer

76 Pressure spring

77 Foot point, left

78 Foot point, right

79 Housing insert

80 Groove

81 Lateral surface

82 Annular insert

83 Stop

84 Brim

85 Edge

86 Mid-region

87 Central region

88 Recesses

89 Annular corner

90 Opening angle

91 Tool

92 Blind bore

93 Shoulder

94 Bore

95 Longitudinal axis

P Pressure medium port

T Tank port

T₁Radial tank port

T₂Axial tank port

A First working port

B Second working port

1. Control valve for influencing the action of a pressure medium on acamshaft adjuster of an internal combustion engine, having a valvehousing (72), a control piston (71) which is arranged in the valvehousing (72) and is axially displaceable under the action of a springelement (pressure spring 76), and a pressure medium port (P), a tankport (T) and two working ports (A, B), wherein, for one axial positionof the control piston (71), a first working port (A) can be connected tothe or a tank port (T2), and the second working port (B) can beconnected to the pressure medium port (P), while for another axialposition of the control piston (71), the second working port (B) can beconnected to the or a tank port (T1) and the first working port (A) canbe connected to the pressure medium port (P), characterized in that thespring element (pressure spring 76) is supported, by means of the footpoint (78) situated at the opposite side from the control piston (71),on a housing insert (79).
 2. Control valve according to claim 1,characterized in that the housing insert (79) has recesses (88), throughwhich the pressure medium can pass out of the control valve (70) inorder to form a port (T2).
 3. Control valve according to claim 2,characterized in that the recesses (88) extend inwards from an outeredge (85) of the housing insert (79).
 4. Control valve according to oneof the preceding claims, characterized in that the housing insert (79)is clipped into the valve housing (72).
 5. Control valve according toclaim 4, characterized in that, in longitudinal section, the housinginsert (79) is approximately in the form of the longitudinal section ofa hat or of a pot, and the “brim” (84) of the hat or the edge (85) ofthe pot is clipped into a groove (80) of an inner lateral surface (81)of the valve housing (72).
 6. Control valve according to claim 5,characterized in that the mid-region (86) of the hat-shaped housinginsert (79) is conical, said mid-region (86) adjoining the brim (84). 7.Control valve according to one of the preceding claims, characterized inthat the diameter of a bore (73) for holding the housing insert (79)approximately corresponds to the diameter of the region for holding thecontrol piston (71) in an axially displaceable fashion.
 8. Control valveaccording to one of the preceding claims, characterized in that thehousing insert (79) forms a stop (83) for the control piston (71), inorder to predefine an axial end position of the control piston (71). 9.Control valve according to one of the preceding claims, characterized inthat the control valve (70) is suitable for being integrated into acamshaft.
 10. Method for producing a control valve for influencing theaction on a camshaft adjuster of an internal combustion engine, inparticular a control valve according to one of claims 1 to 9,characterized by the following method steps: a) forming a bore (73) inthe valve housing (72), said bore (73) being at least of a length whichpermits it to hold both a control piston (71) and also a housing insert(79), b) forming a groove (80) in the bore (73) of the valve housing(72), c) radially compressing a housing insert (79), d) inserting thehousing insert (79), in the radially compressed state, into the bore(73) of the valve housing (72) and e) radially expanding the housinginsert (72) in such a way that the radially outer edge (85) of thehousing insert (79) is received in the groove (80) of the valve housing(72).
 11. Method according to claim 10, characterized in that the bore(73) is formed in the valve housing (72) in the form of a through bore.12. Method according to claim 10 or 11, characterized in that a housinginsert (79) is produced in the form of a “hat”, with a conicalmid-region (86), and the housing insert (79) is radially elasticallyexpanded and compressed by changing the opening angle (90) of theconical mid-region (86).
 13. Method according to claim 12, characterizedin that, in order to insert the housing insert (79) into the valvehousing (72), the housing insert (79) is held in a tool (91) such thatthe opening angle (90) of the conical mid-region (86) is reduced.